1. Field of the Invention
The invention relates to a temperature detection apparatus and a rotation angle detection apparatus.
2. Description of the Related Art
Resolvers have been known which output a voltage signal corresponding to a rotation angle of a rotor. Resolvers have detection accuracy that may vary depending on temperature, and often needs compensation based on the temperature. Thus, to detect the temperature of a resolver, the resolver itself may be used instead of a temperature sensor such as a thermistor. For example, as a method of using the resolver to detect the temperature thereof, a method described in Japanese Patent Application Publication No. 2003-315162 (JP 2003-315162A) is known. JP 2003-315162 A describes calculating a phase difference between phase signals resulting from sine approximation or cosine approximation based on voltage signals for the phases output from the resolver to calculate the temperature from the result of the calculation.
In the method in JP 2003-315162 A, the output values of the voltage signals for the phases output from the resolver are retrieved as plurality of times during one period, and sine approximation or cosine approximation is executed on the retrieved output values to obtain the phase signals. Thus, in the method of JP 2003-315162 A, the temperature is calculated which is based on the output values retrieved at least one period earlier. The method of JP 2003-315162 A may pose no problem depending on the application of the resolver. However, there has been a demand to calculate the temperature in real time, in other words, with substantially no delay.